ECG Comprehensive Resource To Help You Ace Exams
Includes Frequently Tested Questions With ELABORATED
100% Correct COMPLETE SOLUTIONS
Guaranteed Pass First Attempt!! Current Update!!
1. In sinus rhythm, where does electrical activation begin?
a. AV node
b. SA node
c. Bundle of His
d. Purkinje fibres - CORRECT ANSWER b. SA node
Rationale: Sinus rhythm is normal rhythm, with activation starting in the SA node.
2. Which part of the ECG corresponds to the atria?
a. P wave
b. QRS complex
c. T wave
d. ST segment - CORRECT ANSWER a. P wave
Rationale: The P wave is atrial activity, leading to atrial contraction.
3. The QRS complex corresponds to which event?
a. Atrial repolarisation
b. Ventricular repolarisation
c. Ventricular depolarisation
d. Atrial contraction - CORRECT ANSWER c. Ventricular depolarisation
Rationale: The QRS complex represents depolarisation of the ventricles.
4. What does the T wave correspond to?
a. Re-polarisation of the ventricles
b. Depolarisation of the ventricles
c. Re-polarisation of the atria
d. Conduction through the AV node - CORRECT ANSWER a. Re-polarisation of the
ventricles
Rationale: The T wave is ventricular re-polarisation.
5. On a standard ECG, what do one large square and one small square
represent?
,a. Large 0.04 s; small 0.2 s
b. Large 0.2 s; small 0.04 s
c. Large 0.5 s; small 0.1 s
d. Large 1 s; small 0.2 s - CORRECT ANSWER b. Large 0.2 s; small 0.04 s
Rationale: A large square is 200 ms and a small square is 40 ms. Five small squares
make one large square.
6. If each large square is 0.2 s, how many large squares are there in 1
second, and per minute?
a. 5 per second; 300 per minute
b. 3 per second; 180 per minute
c. 10 per second; 600 per minute
d. 5 per second; 150 per minute - CORRECT ANSWER a. 5 per second; 300 per
minute
Rationale: 1 s ÷ 0.2 s = 5 large squares per second, and 5 × 60 = 300 per minute.
7. Where is the PR interval measured from and to?
a. Start of P wave to start of QRS complex
b. Start of P wave to end of T wave
c. End of P wave to end of QRS complex
d. Start of QRS complex to end of T wave - CORRECT ANSWER a. Start of P wave to
start of QRS complex
Rationale: PR runs from the beginning of the P wave to the beginning of the QRS.
Start of QRS to end of T wave is the QT interval.
8. What is the normal PR interval?
a. 40-80 ms (1-2 small squares)
b. 120-200 ms (3-5 small squares)
c. 200-400 ms (5-10 small squares)
d. Greater than 240 ms - CORRECT ANSWER b. 120-200 ms (3-5 small squares)
Rationale: Normal PR is 120-200 ms, up to one large square.
9. The R-R interval is 4 large squares. What is the heart rate?
a. 60 beats per min
b. 75 beats per min
c. 100 beats per min
,d. 150 beats per min - CORRECT ANSWER b. 75 beats per min
Rationale: 4 × 0.2 s = 0.8 s per beat, and 60 ÷ 0.8 = 75 beats per min.
10.Which part of the ECG corresponds to ventricular contraction taking place?
a. P wave
b. PR interval
c. ST segment
d. U wave - CORRECT ANSWER c. ST segment
Rationale: QRS is depolarisation. Contraction follows during the ST segment.
11.A short PR interval indicates which of the following?
a. Delayed conduction through the AV node
b. Abnormally fast conduction from the atria to the ventricles
c. Slow spread of excitation through the ventricles
d. Failure of atrial depolarisation - CORRECT ANSWER b. Abnormally fast
conduction from the atria to the ventricles
Rationale: PR reflects conduction from the SA node through the atria, AV node and
bundle of His into the ventricles. A short PR means abnormally fast conduction.
12.A U wave is an extra wave after the T wave. What does it represent?
a. Depolarisation of the atria
b. Re-polarisation of the papillary muscles
c. Depolarisation of the septum
d. Conduction through the bundle of His - CORRECT ANSWER b. Re-polarisation of
the papillary muscles
Rationale: The U wave represents re-polarisation of the papillary muscles.
13.A prolonged QT interval is worrisome because the patient is at increased risk
of which arrhythmia?
a. Sinus bradycardia
b. Ventricular tachycardia
c. First-degree AV block
d. Atrial ectopics - CORRECT ANSWER b. Ventricular tachycardia
Rationale: QT covers ventricular depolarisation and repolarisation. Prolongation
raises the risk of ventricular tachycardia.
14.Which leads look at the inferior surface of the heart?
, a. aVR and V1
b. I and aVL
c. aVF and III
d. V5 and V6 - CORRECT ANSWER c. aVF and III
Rationale: aVF and III view the inferior surface. I and aVL view the left lateral
surface.
15.Which pairing of chest leads and the area they view is correct?
a. V1 and V2: anterior and lateral left ventricle
b. V3 and V4: right ventricle
c. V5 and V6: septum
d. V1 and V2: right ventricle - CORRECT ANSWER d. V1 and V2: right ventricle
Rationale: V1-V2 view the right ventricle, V3-V4 the septum and anterior left
ventricle, and V5-V6 the anterior and lateral left ventricle.
16.Which lead is usually used to identify the cardiac rhythm, and why?
a. aVR, because deflections are always upward
b. V6, because it views the lateral wall
c. Lead II, because it shows the P wave most clearly
d. Lead III, because it views the inferior surface only - CORRECT ANSWER c. Lead II,
because it shows the P wave most clearly
Rationale: The rhythm lead is whichever shows the P wave most clearly, usually
lead II.
17.A QRS complex is predominantly upward (R wave greater than S wave) in a
lead. What does this mean?
a. Depolarisation is moving toward that lead
b. Depolarisation is moving away from that lead
c. Repolarisation is delayed
d. The lead is placed incorrectly - CORRECT ANSWER a. Depolarisation is moving
toward that lead
Rationale: An upward deflection means depolarisation is moving toward the lead.
Downward (S greater than R) means it is moving away.
18.In a normal ECG, why are the deflections usually downward in aVR but
upward in lead II?
Includes Frequently Tested Questions With ELABORATED
100% Correct COMPLETE SOLUTIONS
Guaranteed Pass First Attempt!! Current Update!!
1. In sinus rhythm, where does electrical activation begin?
a. AV node
b. SA node
c. Bundle of His
d. Purkinje fibres - CORRECT ANSWER b. SA node
Rationale: Sinus rhythm is normal rhythm, with activation starting in the SA node.
2. Which part of the ECG corresponds to the atria?
a. P wave
b. QRS complex
c. T wave
d. ST segment - CORRECT ANSWER a. P wave
Rationale: The P wave is atrial activity, leading to atrial contraction.
3. The QRS complex corresponds to which event?
a. Atrial repolarisation
b. Ventricular repolarisation
c. Ventricular depolarisation
d. Atrial contraction - CORRECT ANSWER c. Ventricular depolarisation
Rationale: The QRS complex represents depolarisation of the ventricles.
4. What does the T wave correspond to?
a. Re-polarisation of the ventricles
b. Depolarisation of the ventricles
c. Re-polarisation of the atria
d. Conduction through the AV node - CORRECT ANSWER a. Re-polarisation of the
ventricles
Rationale: The T wave is ventricular re-polarisation.
5. On a standard ECG, what do one large square and one small square
represent?
,a. Large 0.04 s; small 0.2 s
b. Large 0.2 s; small 0.04 s
c. Large 0.5 s; small 0.1 s
d. Large 1 s; small 0.2 s - CORRECT ANSWER b. Large 0.2 s; small 0.04 s
Rationale: A large square is 200 ms and a small square is 40 ms. Five small squares
make one large square.
6. If each large square is 0.2 s, how many large squares are there in 1
second, and per minute?
a. 5 per second; 300 per minute
b. 3 per second; 180 per minute
c. 10 per second; 600 per minute
d. 5 per second; 150 per minute - CORRECT ANSWER a. 5 per second; 300 per
minute
Rationale: 1 s ÷ 0.2 s = 5 large squares per second, and 5 × 60 = 300 per minute.
7. Where is the PR interval measured from and to?
a. Start of P wave to start of QRS complex
b. Start of P wave to end of T wave
c. End of P wave to end of QRS complex
d. Start of QRS complex to end of T wave - CORRECT ANSWER a. Start of P wave to
start of QRS complex
Rationale: PR runs from the beginning of the P wave to the beginning of the QRS.
Start of QRS to end of T wave is the QT interval.
8. What is the normal PR interval?
a. 40-80 ms (1-2 small squares)
b. 120-200 ms (3-5 small squares)
c. 200-400 ms (5-10 small squares)
d. Greater than 240 ms - CORRECT ANSWER b. 120-200 ms (3-5 small squares)
Rationale: Normal PR is 120-200 ms, up to one large square.
9. The R-R interval is 4 large squares. What is the heart rate?
a. 60 beats per min
b. 75 beats per min
c. 100 beats per min
,d. 150 beats per min - CORRECT ANSWER b. 75 beats per min
Rationale: 4 × 0.2 s = 0.8 s per beat, and 60 ÷ 0.8 = 75 beats per min.
10.Which part of the ECG corresponds to ventricular contraction taking place?
a. P wave
b. PR interval
c. ST segment
d. U wave - CORRECT ANSWER c. ST segment
Rationale: QRS is depolarisation. Contraction follows during the ST segment.
11.A short PR interval indicates which of the following?
a. Delayed conduction through the AV node
b. Abnormally fast conduction from the atria to the ventricles
c. Slow spread of excitation through the ventricles
d. Failure of atrial depolarisation - CORRECT ANSWER b. Abnormally fast
conduction from the atria to the ventricles
Rationale: PR reflects conduction from the SA node through the atria, AV node and
bundle of His into the ventricles. A short PR means abnormally fast conduction.
12.A U wave is an extra wave after the T wave. What does it represent?
a. Depolarisation of the atria
b. Re-polarisation of the papillary muscles
c. Depolarisation of the septum
d. Conduction through the bundle of His - CORRECT ANSWER b. Re-polarisation of
the papillary muscles
Rationale: The U wave represents re-polarisation of the papillary muscles.
13.A prolonged QT interval is worrisome because the patient is at increased risk
of which arrhythmia?
a. Sinus bradycardia
b. Ventricular tachycardia
c. First-degree AV block
d. Atrial ectopics - CORRECT ANSWER b. Ventricular tachycardia
Rationale: QT covers ventricular depolarisation and repolarisation. Prolongation
raises the risk of ventricular tachycardia.
14.Which leads look at the inferior surface of the heart?
, a. aVR and V1
b. I and aVL
c. aVF and III
d. V5 and V6 - CORRECT ANSWER c. aVF and III
Rationale: aVF and III view the inferior surface. I and aVL view the left lateral
surface.
15.Which pairing of chest leads and the area they view is correct?
a. V1 and V2: anterior and lateral left ventricle
b. V3 and V4: right ventricle
c. V5 and V6: septum
d. V1 and V2: right ventricle - CORRECT ANSWER d. V1 and V2: right ventricle
Rationale: V1-V2 view the right ventricle, V3-V4 the septum and anterior left
ventricle, and V5-V6 the anterior and lateral left ventricle.
16.Which lead is usually used to identify the cardiac rhythm, and why?
a. aVR, because deflections are always upward
b. V6, because it views the lateral wall
c. Lead II, because it shows the P wave most clearly
d. Lead III, because it views the inferior surface only - CORRECT ANSWER c. Lead II,
because it shows the P wave most clearly
Rationale: The rhythm lead is whichever shows the P wave most clearly, usually
lead II.
17.A QRS complex is predominantly upward (R wave greater than S wave) in a
lead. What does this mean?
a. Depolarisation is moving toward that lead
b. Depolarisation is moving away from that lead
c. Repolarisation is delayed
d. The lead is placed incorrectly - CORRECT ANSWER a. Depolarisation is moving
toward that lead
Rationale: An upward deflection means depolarisation is moving toward the lead.
Downward (S greater than R) means it is moving away.
18.In a normal ECG, why are the deflections usually downward in aVR but
upward in lead II?
